Chapter 2 Chemical Evolution - The Genesis of the First Organic Compounds

Schwartz, Alan W.

doi:10.1016/s0422-9894(08)70324-6

Cited by 9 publications

(11 citation statements)

References 81 publications

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“…If all of the nitrogen in the Earth's crustal, atmospheric, and ocean reservoirs were present as amino acids dissolved in oceans of the present volume the concentration would be ∼ 0.2 M (Schwartz 1981). This would be the absolute highest possible amino acid concentration which could have been obtained in the primitive oceans.…”

Section: Introductionmentioning

confidence: 83%

An Evaluation of the Critical Parameters for Abiotic Peptide Synthesis in Submarine Hydrothermal Systems

Cleaves

Aubrey

Bada

2008

Orig Life Evol Biosph

102

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It has been proposed that oligopeptides may be formed in submarine hydrothermal systems (SHSs). Oligopeptides have been synthesized previously under simulated SHS conditions which are likely geochemically implausible. We have herein investigated the oligomerization of glycine under SHS-like conditions with respect to the limitations imposed by starting amino acid concentration, heating time, and temperature. When 10(-1) M glycine solutions were heated at 250 degrees C for < 20 min glycine oligomers up to tetramers and diketopiperazine (DKP) were detectable. At 200 degrees C, less oligomerization was noted. Peptides beyond glycylglycine (gly2) and DKP were not detected below 150 degrees C. At 10(-2) M initial glycine concentration and below, only gly2, DKP, and gly3 were detected, and then only above 200 degrees C at < 20 min reaction time. Gly3 was undetectable at longer reaction times. The major parameters limiting peptide synthesis in SHSs appear to be concentration, time, and temperature. Given the expected low concentrations of amino acids, the long residence times and range of temperatures in SHSs, it is unlikely that SHS environments were robust sources of even simple peptides. Possible unexplored solutions to the problems presented here are also discussed.

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Section: Introductionmentioning

confidence: 83%

An Evaluation of the Critical Parameters for Abiotic Peptide Synthesis in Submarine Hydrothermal Systems

Cleaves

Aubrey

Bada

2008

Orig Life Evol Biosph

102

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“…2 Schwartz (1981), prebiotic oceanic ΣCO 2 estimate (130 mM) from Morse and Mackenzie (1998), and prebiotic [NH 3 ] estimates from Summers (1999). The estimates based on atmospheric CO 2 and N 2 levels were calculated using Henry's Law at 25°C.…”

Section: Methodsmentioning

confidence: 99%

“…This would give concentrations of 1-carbon compounds in the primitive ocean of approximately 1 M and a maximum concentrations of oceanic single-nitrogen atom species of ∼0.2 M (Schwartz 1981). More realistic estimates of total primitive oceanic carbon concentrations have been estimated as ∼130 mM, mostly in the form of bicarbonate, based on the amount of CO 2 needed to keep surface water in the liquid state due to the decreased luminosity of the early sun (Morse and Mackenzie 1998).…”

Section: Introductionmentioning

confidence: 99%

The Role of Submarine Hydrothermal Systems in the Synthesis of Amino Acids

Aubrey

Cleaves

Bada

2008

Orig Life Evol Biosph

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There is little consensus regarding the plausibility of organic synthesis in submarine hydrothermal systems (SHSs) and its possible relevance to the origin of life. The primary reason for the persistence of this debate is that most experimental high temperature and high-pressure organic synthesis studies have neglected important geochemical constraints with respect to source material composition. We report here the results of experiments exploring the potential for amino acid synthesis at high temperature from synthetic seawater solutions of varying composition. The synthesis of amino acids was examined as a function of temperature, heating time, starting material composition and concentration. Using very favorable reactant conditions (high concentrations of reactive, reduced species), small amounts of a limited set of amino acids are generated at moderate temperature conditions ( approximately 125-175 degrees C) over short heating times of a few days, but even these products are significantly decomposed after exposure times of approximately 1 week. The high concentration dependence observed for these synthetic reactions are demonstrated by the fact that a 10-fold drop in concentration results in orders of magnitude lower yields of amino acids. There may be other synthetic mechanisms not studied herein that merit investigation, but the results are likely to be similar. We conclude that although amino acids can be generated from simple likely environmentally available precursors under SHS conditions, the equilibrium at high temperatures characteristic of SHSs favors net amino acid degradation rather than synthesis, and that synthesis at lower temperatures may be more favorable.

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“…The free energy of hydrolysis of a peptide bond is estimated by numerous authors as $ 3.5 kcal/mol (Dobry et al, 1952;Meggy, 1956;Flegmann and Scholefield, 1978;Flegmann and Tattersall, 1979;Kahne and Still, 1988;Martin, 1998), corresponding to an equilibrium of dipeptide in a concentrated 1 M amino acid solution of $2.7 Â 10 À3 , 5.9 Â 10 À3 and 3.5 Â 10 À2 M at 25, 70, or 250°C, respectively, assuming no monomer degradation. It should be noted that if all of the nitrogen in the present atmosphere were dissolved in oceans of the present size in the form of glycine, the concentration would be $ 1 M (Schwartz, 1981). At the high end estimate of geochemically plausible amino acid concentration (3 Â 10 À4 M, as discussed above), the equilibrium dipeptide concentrations are 2.4 Â 10 À10 , 5.3 Â 10 À10 and 3.1 Â 10 À9 M at 25, 70 or 250°C, respectively, again assuming no degradation of monomer.…”

Section: Introductionmentioning

confidence: 99%